1. Field of the Invention
The present invention relates to a write-once type storage apparatus in which information is written once in a disk medium, and then repeatedly reproduced, a control method thereof and a record control circuit therefor. More particularly, the invention relates to a write-once type storage apparatus for which the face recording density is improved through optimization of the track pitch, considering variation of the head recording width dependent upon the yaw angle of a rotary actuator.
2. Description of the Related Art
Conventionally, a write-once type storage apparatus uses an optical disk medium such as a DVD which is a portable storage medium, and in an optical disk drive using an optical disk medium, in general, a linear actuator linearly driving an optical head in a direction crossing the medium track is used as a head actuator.
On the other hand, in a hard disk drive using a magnetic disk medium, positioning of the head is accomplished by using a rotary actuator for the magnetic disk medium. Information can be accessed at random at a position of an arbitrary track or continuously. For such a hard disk drive, one usable as a portable storage medium by housing a magnetic disk medium in a cartridge is known.
More recently, it has come to be used in various devices and apparatuses other than information devices along with the tendencies toward a larger capacity, a smaller size and a lower cost. Among others, optical disk drives such as DVD are used also as write-once type storage apparatus in which a movie or music is once written in, and which are thereafter used exclusively for reproduction.
In the case of a conventional write-once type hard disk drive, it is the usual practice to continuously write information, with the outermost track as the starting track, in a direction toward the inner side in a run of the write processing.
However, in such continuous recording in a single direction in the conventional write-once type storage apparatus, a relatively wide track pitch is usually used in consideration of the head inclination resulting from an increase in the yaw angle of the rotary actuator, and this leads to a problem of impossibility to increase the face recording density of magnetic disk medium.
That is, if a track pitch is selected, depending upon the head width, for example, at a position with a yaw angle of 0° without taking into account the head inclination caused by the yaw angle, the head widens over the track width under the effect of head inclination at a head position where the yaw angle increases on the outer side or on the inner side. A write operation in this state causes the portion sticking out the track width to overwrite the adjacent track, thus destroying information already recorded in the adjacent track and leading to a lower error rate. This may result in impossibility to read out the information.
A wider track width is used to avoid this inconvenience so that an increase in the yaw angle does not interfere in the adjacent track. It is therefore difficult to increase the face recording density by reducing the track pitch over this limit.